1. Field of the Invention
The present invention relates to a fuel tank arrangement of a motorcycle and, in particular, to a fuel tank arrangement having no effect on a riding position.
2. Description of the Background Art
One example of a fuel tank arrangement structure of a motorcycle is disclosed in Japanese Utility Model Laid-Open No. 63-18391/1988A. The motorcycle includes a pair of left and right main frames extending obliquely downwardly and rearwardly from a head pipe. A pair of left and right seat rails extend obliquely upwardly and rearwardly from the rear ends of the pair of left and right main frames. A fuel tank is supported on the main frames, and a seat is supported on the seat rails at the back of the fuel tank. The front ends of the seat rails are connected to the middle portions of the main frames, and the fuel tank is located on both the main frames and seat rails. The fuel tank is supported by the front portion of the seat to hold the position of the rear side of the fuel tank nearly horizontal.
In this connection, the fuel tank tends to be increased in width, height, and length to ensure a predetermined volume, which results in increasing the size of the vehicle body. However, the fuel tank of a motorcycle needs to have, at its rear portion, a knee-grip portion which a rider grips with his knees. Hence it is necessary to ensure that the fuel tank permits a riding position where the rider easily grips the fuel tank with his knees. However, the above fuel tank having an increased size cannot fulfill the above requirements, and sometimes has a negative effect on the riding position of the rider. For this reason, it is the object of the present invention to solve the above problem.
It is therefore an object of the present invention to provide a fuel tank arrangement structure of a motorcycle having a pair of left and right main frames extending obliquely downwardly and rearwardly from a head portion at the front end, and a pair of left and right seat rails extending obliquely upwardly and rearwardly from the rear end portions of the main frames.
A fuel tank is supported on the main frames, and a seat is supported on the seat rails behind the fuel tank. In the present invention, the rear end portion of the fuel tank is formed into an extension extending rearwardly behind the rear end portions of the main frames. The extension of the fuel tank has a narrower width than a main body of the fuel tank, and is arranged under the seat and between the left and right seat rails. This enables the volume of the fuel tank to expand into the extension under the seat, which can reduce the width, the height and the length of the front portion of the fuel tank in front of the seat, while ensuring a predetermined volume of the fuel tank.
As a result, the narrower width of the fuel tank located forwardly of the seat makes it easier for a rider to grip the tank with his knees and to assume a good riding position. Further, the fuel tank extension arranged under the seat can lower the center of gravity of the vehicle body. In addition, the seat rails act as the members protecting the extension.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.